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KNH 381 Project Wiki
The Basics of Soccer To play the game of soccer, all you essentially need is a ball and a few people to form two separate teams. This makes the game very inexpensive to play and is one of the many fac tors that has made it so popular around the world. The basic idea of the game is to move the soccer ball down the field, past defending players, and kick the ball into the opposig goal to score a point. Players move the ball down the field by passing, dribbling, and kicking the soccer ball. Each team's goalie attempts to stop the ball from entering the goal by using their hands or arms. Most of the ball handling is done by the players on the field using their feet to kick the ball into the goal. The field players may also use their head and torso to intercept or complete a pass. To get the ball down the field efficiently, kicking the ball is a skill each player (even the goalie) on the field needs to master. Kicking a soccer ball involves the motion of one leg to kick a ball, which will propel it forward. While most people know the basic idea of soccer, and specifically the soccer kick, not many people consider the physics behind the important movement. Want to learn more? The following website discusses the basic rules of the game: http://www.upperdublinsoccerclub.org/docs/RECREATION/17_Rules/17%20Rules%20of%20Soccer%20Soccer.pdf Category:Browse Movement Phases of a Soccer Kick '1. Starting Position ' Take a few steps away from the ball and approah from a slight angle. This allows the player to build momentum and finish with a powerful kick. Once a small distance between the player and the ball is established, the left foot should be positioned approximately one foots length in front of the right (kicking foot). Make sure your body is in a standing upright position. '2. Planting Your Foot ' Once you have the proper starting position and begin moving towards the soccer ball you must plant your foot. The planter foot is the foot you're not kicking with. The planter foot is on the same horizontal plane as the soccer ball. Planting your foot behind or in front of the ball can result in a less powerful kick. This phase determines the direction of the kick, so where you aim your planter foot corresponds to the direction the ball will travel. Planting your foot is done in the sagittal plane and is comprised of knee extension and plantar flexion. '3. Backswing of Leg' The backswing of your leg generates the force behind the kick. In this phase the player determines how much speed and powe r they intend to kick with, and transfer this power to the forward swing phase. For passing, only bring your leg back a small amount. For a long distance kick, extend your leg back much further and bend your knee. This movement includes posterior abduction of your right leg and drawing it back as far as you can to gain maximum power. '4. Forward Swing of Leg (Acceleration)' The acceleration of your kicking leg corresponds to how fast the player moves his/her leg forward and through the soccer ball. Thi s is an explosive anaerobic movement. It consists of adduction of your right leg, increasing speed as your right foot approaches the soccer ball. Your right foot then makes contact with the ball with knee fully extended. At ball contact hips are flexed, plantar flexion in kicking foot, and slight dorsiflexion in planted foot. Your right leg surpasses your left leg and continues forward. Torque and moment arm play a role in this phase. The longer the limb and the shorter the moment arm, the higher velocity will be generated. '5. Follow-Through of Leg ' The follow-through is the continuation of the kick after contact with the ball has been made. This movement involces full anterior abduction of your right leg extended out in front of you. Your hip and knee should be flexed in this phase. It ends in a slight medial rotation, which is also known as the final follow-through Want to learn more? The following website has a more detailed analysis of each movement: http://www.sportsinjurybulletin.com/archive/biomechanics-soccer.htm# Soccer Kick Adjustments The movement phases of the soccer kick described above describe the side-foot techiquee, which is very common. The side-foot technique allows the kicker to have more control over where the ball will travel, at what speed, and at what angle. One study published in 2009 found that, "the impact point is more influential on the ball's velocity than the attack angle and the attack angle is more influential on the ball's rotation than the impact point" (Impact Dynamic Theory, 2009). This study had the soccer players, who were experienced players at the collegiate level, use the side-foot technique when kicking a soccer ball. The side-foot technique increases the amount surface area contact between the foot and the ball, which is the main reason the kicker has greater control as to where the ball goes. Depending on the skill level of the player, the attack angle the player chooses to use will alter the position and motion of the ball. This can cause the ball to travel far distances, curve, etc. The side-foot technique would be ideal for soccer players to use to improve the amount of force and accuracy applied to the ball. While another technique may provide more force, the side-foot technique provides the best balance between force exerted on the ball and its resulting accuracy. Soccer Kick In-Depth Breakdown Ideal Muscle Activation for Accuracy The muscles of the leg play an important role in the accuracy and trajectory of a soccer kick. A study performed in May of 2012 tracked the muscle activation patterns of soccer players while they kicked a soccer ball at two different targets into a soccer goal. One target was positioned high and the other was positioned low in the goal. The researchers told each soccer player what to aim for and tracked the accuracy of their kick. Depending on each soccer player's kick technique certain muscles were activated in the leg that seem to have made the soccer players more accurate. Specifically, the experiment analyzed "the activation of tibialis anterior (TA), rectus femoris (RF), biceps femoris (BF) and gastrocnemius muscle (GAS) of the swinging leg and the ground reaction forces (GRFs) of the support leg. The GRFs did not differ between kicking conditions. There was significantly higher TA and BF and lower GAS EMG activity during accurate kicks to the top target compared with inaccurate kicks. Furthermore, there was a significantly lower TA and RF activation during accurate kicks against the bottom target compared with inaccurate kicks" (Mechanisms, 2012). This study found that if a technique is utilized to increase the activation of the tibialis anterior and biceps femoris, while lowering the gastrocnemius activity during the kick, the player could have more accurate kicks to higher areas of the goal, and should lower tibialis anterior and rectus femoris activity during lower goal kicks. The Physics of a Soccer Kick Newton's Laws of Motion At rest, the soccer ball is motionless. According to Isaac Newton's First Law of Motion, the ball will remain motionless until an outside force is applied to it. Once a force is applied to the ball, the ball will remain in motion until acted on by another force. The outside force that would stop the ball, or alter it's motion, could be another player, the goal, an object, friction, or any other external force. How fast the ball is moving, with how much force the ball is moving, and how much force would be required to stop the ball (or how an outside force would alter the ball's path) all depend on Newton's Second Law of Motion. Isaac Newton's Second Law discerns that the force an object moves with is determined by its mass (in kilograms), and it's acceleration (m/s2). This results in the formula, Force = mass x acceleration (F = ma), with force being measured in Newtons (N or kg x m/s2). Newton's Third Law of Motion, which states that for every action there is an equal and opposite reaction, accounts for with how much force a ball will move and in what direction. This is determined by the initial placement of the ball, whether or not it is in motion, the force of the soccer kick itself, and the angle with which it is kicked. With this formula, acceleration is considered the change in velocity divided by the change in time. This results in the formula F= m (v/t). Due to the nature of Newton's Third Law, it is determined that the initial force of the first object will transfer to the final object with the formula F1i = m1v1 = m2v2 = F2f. Magnus Effect A skill many experienced soccer players have is "curving" and/or "bending" the ball. If you are unfamiliar with curving the soccer ball, take a look at this informational video below. To curve the ball, the player needs to kick the ball slightly off center, causing it to spin horizontally. Any time the soccer ball is kicked, air moves over the ball. When a player curves a soccer ball, the air moving over the ball moves faster around one side, which creates less pressure on that same side of the ball. In other words, the faster speed of air corresponds to lower pressure. On the opposite side of the ball the air moves slower, creating a higher pressure. The air moves slower on this side because the spin is going against the air flow. The ball is pushed in the direction from high pressure to low pressure and results in a curved path. This phenomenon is known as the Magnus Effect. If you notice in the video the ball doesn't curve immediately after it is kicked. The ball will go straight for a little while because when it is kicked the ball travels quickly and there is a lack of air resistance. Once it loses velocity and slows down, the Magnus effect occurs and air flow starts to curve it. Kinetic Energy Citations 1.) De Witt, J. K., & Hinrichs, R. N. (2012). Mechanical factors associated with the development of high ball velocity during an instep soccer kick. Sports Biomechanics, 11(3), 382-390. 2.) (Impact Dynamic Theory, 2009) Ishii, H., Yanagiya, T., Naito, H., Katamoto, S., & Maruyama, T. (2009). Numerical study of ball behavior in side-foot soccer kick based on impact dynamic theory. ''Journal of Biomechanics,''2712-2720. 3.) (Mechanisms, 2012) Katis, A., Giannadakis, E., Kannas, T., Amiridis, I., Kellis, E., & Lees, A. (2012). Mechanisms that influence accuracy of the soccer kick. ''Journal of Electromyography and Kinesiology,''125-131. Photos and videos are a great way to add visuals to your wiki. Find videos about your topic by exploring Wikia's Video Library. Category:Browse